NEW YORK (AP) -- Nearly a half century after she broke one of tennis' racial barriers, Althea Gibson admired the artistry and power of the Williams sisters at the U.S. Open.

``I would like to congratulate the Williams family for accomplishing this historic achievement,'' Gibson was quoted in The New York Times on Sunday. ``Two family members and two sisters who have become two of the greatest tennis athletes in the world.''

The 74-year-old Gibson watched on television Friday as Venus and Serena Williams won their semifinals, setting up the first Grand Slam final between sisters in 117 years. It was also the first time two blacks played in a Grand Slam singles final.

Gibson watched from her apartment in East Orange, N.J., and spoke through spokeswoman and friend Fran Gray. Gray is president and chief executive officer of the Althea Gibson Foundation.

Gibson was most pleased by the versatility the sisters showed in defeating Martina Hingis and Jennifer Capriati in straight sets.

``In the beginning, Venus played with only brute force,'' Gibson told the Times. ``You've harnessed you power and combined it with finesse and variety now.''

In 1957, Gibson -- a powerful serve-and-volley player -- became the first black to win the Wimbledon singles title and the first to win the U.S. national crown.